Set a couple years before 1900, the scene is set on Devil's Island (at the time a French colony that included a notorious prison) and we're introduced to our three protagonists, Joseph, Albert and Jules. They're escaped convicts who offer to repair the roof of a store with the intent of robbing the place as soon as possible to finance their departure from the island. Joseph (Humphrey Bogart) was in jail for cooking some books: he's very good at it (although he clearly got caught) and is also exceptionally good at selling people stuff they don't need. Albert (Aldo Ray) really likes the ladies - but was in for beating his uncle to death when he wouldn't give Albert the money he needed. Jules (Peter Ustinov) is the break-and-enter man and safe-cracker, who can open anything. But before they get to robbing the family that owns the store attached to the roof they're not actually fixing, they get to know the family - who are rather nice people with some unpleasant troubles on their hands.
It was directed by Michael Curtiz (best known these days for "Casablanca") and stars Bogart in a comedy role - not something he did often. It's a little quaint and goofy, but I found it surprisingly funny and really enjoyed it.